Laevichlamys limatula (Reeve, 1853)

Dijkstra, Henk H. & Beu, Alan G., 2018, Living Scallops of Australia and Adjacent Waters (Mollusca: Bivalvia: Pectinoidea: Propeamussiidae, Cyclochlamydidae and Pectinidae), Records of the Australian Museum (Rec. Aust. Mus.) 70 (2), pp. 113-330 : 243

Laevichlamys limatula (Reeve, 1853)

Figs 66, 67E,K–L, 69G,J

Pecten limatula Reeve, 1853 : sp. 124, pl. 28, fig. 124; Küster & Kobelt, 1888: 257, pl. 67, fig. 5; Melvill & Standen, 1899: 183.

Pecten (Chlamys) limatula Reeve. –Dautzenberg & Bavay, 1912: 12.

Laevichlamys limatula (Reeve) .– Waller, 1993: 204; Raines & Poppe, 2006: 204–205, upper figs; pl. 144, figs 2a–b; Dijkstra & Moolenbeek, 2008: 19.

Type data. Holotype (pr) NHMUK1981246 , figured by Reeve (1853: pl. 28, fig. 124), refigured by Raines & Poppe (2006: pl. 144, figs 2a–b). Type locality: Unknown.

Additional material examined. —AUSTRALIA: QUEENSLAND: GBR, No. 8 Sand Cay, N side, 13°21'S 143°57'E,dead, 4–21 m (1 v, C.157597); GBR, Swain Reefs, Reef 21-176, N slope, 21°20'S 151°36'E, dead, 10 m (1 v, C.332602). WESTERN AUSTRALIA: Abrolhos Islands ,Wallabi Group, E side of Goss Passage, Beacon Island, approx. 28°28'S 113°45'E,dead,subtidal (2 pr, WAM S30731 );Abrolhos Islands ,Wallabi Group, E side of Beacon Island, approx. 28°28'S 113°47'E, dead, 6–27 m (1 v, WAM 490.91);Abrolhos Islands ,Wallabi Group,SW of Dicks Island,Noon Reef, approx. 28°28'S 113°45'E,alive, 2–3 m (1 pr, WAM 491.91).—CHRISTMAS ISLAND: Flying Fish Cove,dead, 5–25 m (1 pr, ZMA Moll.146222).—MARSHALL ISLANDS : Kwajalein Atoll, Carlos Island, outside lagoon, alive, 15 m (1 pr, ZMA Moll.142482); Kwajalein Island, ocean side of reef, alive, 12–18 m (3 pr, ZMA Moll.142478).—FIJI ISLANDS : Viti Levu, Beqa Island, alive, 18 m (1 pr, ZMA Moll.142486). —LINE ISLANDS : Christmas Island, Cook Isle, alive, 12 m (6 pr, ZMA Moll.142487).

Description. Shell up to c. 30 mm high, thin, semitranslucent, ovate, some specimens prosocline, others acline; valves almost equally weakly inflated, slightly inequivalve, equilateral, auricles highly unequal in shape and size, umbonal angle c. 85–90°; brightly coloured, cream, orange or yellow with radial blotched streaks of darker colour; some specimens uniformly coloured.

Both valves sculptured with numerous, very closely and unevenly spaced, spinous radial riblets (c. 60–70 in adult stage near ventral margin), increasing by intercalation and varying slightly in prominence. Interstitial microsculpture commarginal in early growth stage, more antimarginal in late ontogeny. Anterior auricles with 6–10 squamous radial riblets, posterior ones with 4–6. Byssal notch relatively deep, byssal fasciole broad. Functional ctenolium well-developed, with 4–6 teeth.

Dimensions. Illustrated specimen: WA, Abrolhos Islands , Wallabi Group, E side of Goss Passage, Beacon Island, approx. 28°28'S 113°45'E ( WAM S30731 ): H 25.2, L 22.3, D 7.6 mm .

Habitat. Living in the littoral zone, byssally attached to the undersides of coral boulders, or amongst coral rubble on clean sand.

Distribution. Tropical Indo-West Pacific, from the Philippines to northern Australia, westwards to Christmas Island, and eastwards into the central Pacific to the Line Islands (Raines & Poppe, 2006: 204); Indonesia, 10–25 m, dead (Dijkstra & Moolenbeek, 2008: 19). Maximum depth range of live-taken specimens is 12– 18 m. Present specimen from Australia alive at 2– 3 m.

Remarks. The epithet “limatula” (Latin, diminutive of “lima”, a file) is an indeclinable noun. The present specimens from Australia are indistinguishable from the holotype.

Wagner (1982: 86) synonymized the present species with Laevichlamys irregularis ( Sowerby, 1842) (= Laevichlamys cuneata (Reeve, 1853) , above), and considered that there are no significant morphological differences between the two nominal taxa. However, L. limatula has much finer and more evenly arranged radial sculpture than L. cuneata , which has much more unevenly spaced and less well-developed narrow and broad radial costae. Moreover, L. limatula is smaller in size, relatively thin, and more brightly coloured. Waller (1993: 204) placed both species in his new genus Laevichlamys .